1 Answer

+2 votes

The answer is d) The speed increases at an increasing rate or the acceleration of the rocket keeps on increasing with time.
This is because of Newton's Third Law of Motion.
(Mass of Rocket)*(Acceleration of Rocket) = (Mass flow rate of the exhaust gases)*(Velocity of the exhaust gases)
Since all the terms in the RHS of the above equation remain constant and the mass of the rocket keeps on falling, to balance out the equation the acceleration of the rocket has to increase.
That is why a rocket starts off moving slowly and goes faster and faster as it climbs into space

A tap is opened to fill a bucket, and water flows from the tank through a pipe. Now, as shown in the diagram, consider two points A and B on the vertical part of the pipe which has a uniform cross section.

If the pipe is completely filled with water and the water flows steadily, then at which point is the speed of the water flow greater?

There is a 50m long army platoon marching ahead. The last person in the platoon wants to give a letter to the first person leading the platoon. So while the platoon is marching he runs ahead, reaches the first person and hands over the letter to him and without stopping he runs and comes back to his original position. In the mean time the whole platoon has moved ahead by 50m.

The question is how much distance did the last person cover in that time. Assuming that he ran the whole distance with uniform speed.

A helium balloon leaves the ground at a point A and rises vertically at uniform speed.
At the end of 5 minutes, Rohan finds the angular elevation of the balloon as 30 degree.
If the point at which Rohan is standing is 550 m away from point A, what is the speed of the balloon in m/s?